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  • 24V trolling motor solar help!

    New to Solar. Building a 8x12 mini pontoon boat.


    I am looking for a complete system that will charge a 24V trolling motor battery set up.

    Trolling Motor: Minn Kota PowerDrive 70lbs V2

    Motor amp draw: 42 amp

    Proposed batteries: I'll get 2 - 12V 100Ah SOLAR WIND AGM SLA DEEP CYCLE VRLA BATTERY I will hook these up in series to obtain 24V

    I can fit probably 6 panels.

    What I am looking to do is charge these batteries throughout the day as I am running the boat. I am not sure at all if it is possible to just run the motor off straight solar or not. I would love to do that but doubt I can pull 42 amps from 6 panels.

    However I go I would like the latest MPPT controller in this kit.

    Would it be possible to have a switch that would either charge the batteries or run the motor.

    Sorry I am new just looking for some help anyone willing

    thanks!


  • #2
    First off I do not believe 2 x 12v 100Ah batteries will run that trolling motor more than a couple of hours before it died. That thing is rated about 1000Watts (42A x 24V = 1008W) and the batteries have only 2400watt hour using 100% of its charge.

    Depending on the wattage of those 6 panels my you could charge a much bigger battery system which you will need to run that motor even a few hours.

    As for running loads or that motor directly from the panels. You do not need a switch if the batteries are fully charged then the power from the charge controller goes directly to the load or your motor.

    The problem is having a battery system big enough to run that motor and then enough solar wattage to charge it back up and maybe have a little left over. With a boat the issue is that unless you can point those panels directly at the sun for hours at a time then they will not produce much in the way of charging or running that motor. Even if you anchor the movement of the boat will reduce the efficiency of those panels.

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    • #3
      You will need more battery - try 4, 6V golf cart batteries, will get you about 24V @ 200 ah storage (100ah useable)

      PV panels. well, how much can you afford ? That motor sucks a lot of power, and your batteries still need charging. Maybe a "hybrid" setup,
      with a small inverter genset charging the battery bank ??? Think and research more.
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

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      • #4
        Thanks SunEagle.... I have not bought the motor just doing research now. I can go to a lower motor but I need 45-50lbs thrust, looks like even lower they still draw about 42amps. I've only looked at Minn Kota's though. So I want to get your point straight in my mind. Lets say it is a completely sunny cloudless day. The panels are facing the sun. Are you saying the movement of the boat decreases the efficiency of the panel?

        Would I need 1000watts of panels to make this worthwhile?

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        • #5
          Originally posted by madtabula View Post
          Thanks SunEagle.... I have not bought the motor just doing research now. I can go to a lower motor but I need 45-50lbs thrust, looks like even lower they still draw about 42amps. I've only looked at Minn Kota's though. So I want to get your point straight in my mind. Lets say it is a completely sunny cloudless day. The panels are facing the sun. Are you saying the movement of the boat decreases the efficiency of the panel?

          Would I need 1000watts of panels to make this worthwhile?
          Depending on the angle of the sun any movement of the panels and where they are being aimed can reduce the effectiveness of a solar panel's production. Heck even a fixed mount is easily affected by a light cloud formation or any type of shade caused by an object like the mast of a sailboat.

          Try to remember that the solar pv nameplate is based on the optimum lab conditions using repeatable conditions. In real life most solar pv never produce what they are rated.

          Well 1000watts at 24volt "should" produce ~ 42amps but for how long and at what efficiency? Maybe you could run that motor using 2000 watts.

          Comment


          • #6
            Your motor pulls 24V 42A, that's 1008W. Being flat on the boat isn't the standard test condition, but you will be in the summer with the high sun, and getting reflecting sun off the water, so let's say you lose 25% by not pointing right at the sun. Add that to other losses, and you are probably down to actually getting about 50% of the rated power of the panels. There are 24V 320W panels available, so 6 of them would generate 1920W x 50% losses = 960W / 24V = 40A. So it would be close, theoretically, and only on perfect days mid day. You'd be much better off storing it in the battery bank.
            On to the battery bank, how long do you intend to be boating? 42A x 1 hour = 42Ah per hour. You never want to use more than half the battery storage, so x 2 = 82Ah 24V battery bank per hour you intend to boat. So the 100Ah battery bank you are proposing will last just over an hour. Yes, you will have the solar array recharging as you are using it, but if the sun goes away, you are stuck out in the middle of the lake without a motor after an hour. Bring a paddle. If you do have an almost 2000W solar array, the amount of current into the battery bank is far too much. Even at half the output, you are talking about 42A into 100Ah battery, that's just over a C-2 rate. Depending on the battery, you don't want to charge faster than C-4 or C-6, so to handle the 42A, you should have at least a 200Ah battery bank.
            Solar Queen
            altE Store

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            • #7
              You need 2000 watt panels.

              If you are lucky, you might get 2 hours run time in a day before the batteries jump overboard to save their lives from abuse. Now you know why there are no solar powered boats, planes, trains, and automobiles.
              Last edited by Sunking; 05-23-2016, 08:00 PM.
              MSEE, PE

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              • #8
                Everyone... thank you so much for the insight. I may rethink this and go with a small gas outboard.... I still need a few panels just for a nice charging station for my camera equipment but I guess I am not gonna run the boat off of solar

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                • #9
                  Originally posted by madtabula View Post
                  Everyone... thank you so much for the insight. I may rethink this and go with a small gas outboard.... I still need a few panels just for a nice charging station for my camera equipment but I guess I am not gonna run the boat off of solar
                  I have seen a number of boats have one or two panels mounted somewhere on their cabins. My guess is that they charge a small battery system that could be used for small loads but I doubt for they are used even for a small trolling motor.

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